Same issue is happening with me too since enabling column mapping. Files are stored in folders with random 2 character names (0P, 3h, BB) rather than the date value of the load_date partition column (load_date=2023-01-01, load_date=2023-01-02).

Have tried using databricks runtime 12.0 but get the same result when performing an append or merge operation. Has anyone been able to resolve this yet?